Fix seed type & feature importance column

[kelly-sovacool]

Thanks to @ehb64 for reporting these issues! 👋🏻

Issues

• Resolves Issue with wildcards$seeds as.double #44.
• Resolves Issue with "names" in plot_feature_importance.R #45.

Change(s) made

• Make sure seed from get_wildcards_tbl() is numeric for proper joining in the train_ml and find_feature_importance rules.
• mikropml v1.6.0 introduced a breaking change: in the output of find_feature_importance the names column was changed to feat. The feat_df column name is changed accordingly here in the plot_feature_importance rule.

Checklist

(Strikethrough any points that are not applicable.)

• Update the docs if there are any API changes (README.md, config/README.md, & quick-start.md).
• Re-run the pipeline on an HPC and update the example report.
• The checks succeed on your most recent commit. This is always required before the PR can be merged.